The overall object of the proposed research is to assure a continuing year round supply of fertile purple sea urchins (Strongylocentrotus purpuratus) as a research resource. The approach to this study is at two levels. Primarily, there will be a close examination of the fertility of sea urchins derived from a special deep water site as a function of season. In general it is known that sea urchins are fertile for several months during the year, and we intend to extend this knowledge to a more precise and detailed level for the chosen locality, the Pt. Loma kelp bed near San Diego, Calif. The new projects in this renewal application include development of methods for identifying stages of oogenesis; measuring the performance of cultured sea urchins with respect to their maintenance of normal annual cycles of oogenesis; measurement of the ability of various collected populations of gravid sea urchins to produce practical quantities of mature oocytes repetitively during maintenance in the culture system; comparative studies of inbreeding and reproductive behavior in isolated micropopulations of sea urchins, utilizing a new, extremely sensitive method of detecting DNA sequence heterogeneity; mapping of selected areas of the Pt. Loma bed to determine environmental correlations with the reproductive heterogeneity known to exist there; experimentation with environmental variables affecting the annual cycles of sea urchin oogenesis in the culture system.